A study to test the hypothesis that insulin resistance results in increased lipid peroxides/oxidative stress, which predisposes pregnant women to the development of preeclampsia. Preeclampsia, or toxemia of pregnancy, is a major cause of medical problems in pregnant women and newborns. It can cause high blood pressure, in the mother, which can lead to kidney and liver problems, seizures, and even death. It can cause low birth weight and delivery problems. The cause is not fully understood and a method of prevention has not been discovered. The patients in this study will have been screened and found to have higher than normal insulin levels. This is an indication that the patient may be at increased risk of developing preeclampsia. Participation in this study will help investigators devise a screening test for women at risk and will help them better understand the cause of preeclampsia, therefore prevention and even a cure may be discovered. Normal prenatal care will occur. At 28 weeks of pregnancy, during the normal test for diabetes (Glucola Challenge Test), additional blood will be drawn (approx. two tablespoons). Additional blood samples will be drawn at 31 and 34 weeks, at the time of delivery, and at the post-partum check up. These blood tests will measure various substances in the blood that may be involved in the development of preeclampsia. After delivery, a sample of the placenta will be evaluated to determine if it produces substances that contribute to preeclampsia problems.